Re: [PATCH 1/2] i3c: Add basic HDR support

[Joshua Yeong]

Hi Mukesh and Frank,

On 02-Feb-2025 1:54 AM, Mukesh Kumar Savaliya wrote:
> Hi Frank,
> 
> On 1/30/2025 1:35 AM, Frank Li wrote:
>> I3C HDR requires enter/exit patterns during each I3C transfer. Add a new
>> API i3c_device_do_priv_xfers_mode(). The existing
>> i3c_device_do_priv_xfers() now calls i3c_device_do_priv_xfers_mode(I3C_SDR)
>> to maintain backward compatibility.
>>
>> Introduce a 'cmd' field in 'struct i3c_priv_xfer', using an anonymous union
>> with 'rnw' since HDR mode relies on read/write commands instead of the
>> 'rnw' bit in the address as in SDR mode.
>>
>> Add a priv_xfers_mode callback for I3C master drivers. If priv_xfers_mode
>> is not implemented, fallback to SDR mode using the existing priv_xfers
>> callback.
>>
>> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
>> ---
>> Why not add hdr mode in struct i3c_priv_xfer because mode can't be mixed in
>> one i3c transfer. for example, can't send a HDR follow one SDR between
>> START and STOP.
>>
> Is it wise to add two function inside main funcion and separate SDR vs HDR ? so we don't need to change current function arguments.

I think the 'private transfers' are limited to SDR communications,
would it be better if we have a different interface/naming for hdr transfers?

>> i3c_priv_xfer should be treat as whole i3c transactions. If user want send
>> HDR follow SDR, should be call i3c_device_do_priv_xfers_mode() twice,
>> instead put into a big i3c_priv_xfer[n].
>> ---
>>   drivers/i3c/device.c       | 19 +++++++++++++------
>>   drivers/i3c/internals.h    |  2 +-
>>   drivers/i3c/master.c       |  8 +++++++-
>>   include/linux/i3c/device.h | 12 +++++++++++-
>>   include/linux/i3c/master.h |  3 +++
>>   5 files changed, 35 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/i3c/device.c b/drivers/i3c/device.c
>> index e80e487569146..e3db3a6a9e4f6 100644
>> --- a/drivers/i3c/device.c
>> +++ b/drivers/i3c/device.c
>> @@ -15,12 +15,13 @@
>>   #include "internals.h"
>>     /**
>> - * i3c_device_do_priv_xfers() - do I3C SDR private transfers directed to a
>> - *                specific device
>> + * i3c_device_do_priv_xfers_mode() - do I3C SDR private transfers directed to a
>> + *                     specific device
>>    *
>>    * @dev: device with which the transfers should be done
>>    * @xfers: array of transfers
>>    * @nxfers: number of transfers
>> + * @mode: transfer mode
>>    *
>>    * Initiate one or several private SDR transfers with @dev.
>>    *
>> @@ -32,9 +33,9 @@
>>    *            driver needs to resend the 'xfers' some time later.
>>    *            See I3C spec ver 1.1.1 09-Jun-2021. Section: 5.1.2.2.3.
>>    */
>> -int i3c_device_do_priv_xfers(struct i3c_device *dev,
>> -                 struct i3c_priv_xfer *xfers,
>> -                 int nxfers)
>> +int i3c_device_do_priv_xfers_mode(struct i3c_device *dev,
>> +                  struct i3c_priv_xfer *xfers,
>> +                  int nxfers, enum i3c_hdr_mode mode)
> why can't we pass mode as another structure member inside struct i3c_priv_xfer ? Adding function agrument parameter impacts existing drivers.
>>   {
>>       int ret, i;
>>   @@ -47,11 +48,17 @@ int i3c_device_do_priv_xfers(struct i3c_device *dev,
>>       }
>>         i3c_bus_normaluse_lock(dev->bus);
>> -    ret = i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers);
>> +    ret = i3c_dev_do_priv_xfers_locked(dev->desc, xfers, nxfers, mode);
>>       i3c_bus_normaluse_unlock(dev->bus);
>>         return ret;
>>   }
>> +EXPORT_SYMBOL_GPL(i3c_device_do_priv_xfers_mode);
>> +
>> +int i3c_device_do_priv_xfers(struct i3c_device *dev, struct i3c_priv_xfer *xfers, int nxfers)
>> +{
>> +    return i3c_device_do_priv_xfers_mode(dev, xfers, nxfers, I3C_SDR);
>> +}
>>   EXPORT_SYMBOL_GPL(i3c_device_do_priv_xfers);
>>     /**
>> diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
>> index 433f6088b7cec..553edc9846ac0 100644
>> --- a/drivers/i3c/internals.h
>> +++ b/drivers/i3c/internals.h
>> @@ -16,7 +16,7 @@ void i3c_bus_normaluse_unlock(struct i3c_bus *bus);
>>   int i3c_dev_setdasa_locked(struct i3c_dev_desc *dev);
>>   int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
>>                    struct i3c_priv_xfer *xfers,
>> -                 int nxfers);
>> +                 int nxfers, enum i3c_hdr_mode mode);
>>   int i3c_dev_disable_ibi_locked(struct i3c_dev_desc *dev);
>>   int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
>>   int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
>> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
>> index d5dc4180afbcf..67aaba0a38db2 100644
>> --- a/drivers/i3c/master.c
>> +++ b/drivers/i3c/master.c
>> @@ -2945,7 +2945,7 @@ int i3c_dev_setdasa_locked(struct i3c_dev_desc *dev)
>>     int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
>>                    struct i3c_priv_xfer *xfers,
>> -                 int nxfers)
>> +                 int nxfers, enum i3c_hdr_mode mode)
>>   {
>>       struct i3c_master_controller *master;
>>   @@ -2956,9 +2956,15 @@ int i3c_dev_do_priv_xfers_locked(struct i3c_dev_desc *dev,
>>       if (!master || !xfers)
>>           return -EINVAL;
>>   +    if (master->ops->priv_xfers_mode)
>> +        return master->ops->priv_xfers_mode(dev, xfers, nxfers, mode);
>> +
>>       if (!master->ops->priv_xfers)
>>           return -ENOTSUPP;
>>   +    if (mode != I3C_SDR)
>> +        return -EINVAL;
>> +
>>       return master->ops->priv_xfers(dev, xfers, nxfers);
>>   }
>>   diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
>> index b674f64d0822e..7ce70d0967e27 100644
>> --- a/include/linux/i3c/device.h
>> +++ b/include/linux/i3c/device.h
>> @@ -40,11 +40,13 @@ enum i3c_error_code {
>>     /**
>>    * enum i3c_hdr_mode - HDR mode ids
>> + * @I3C_SDR: SDR mode (NOT HDR mode)
>>    * @I3C_HDR_DDR: DDR mode
>>    * @I3C_HDR_TSP: TSP mode
>>    * @I3C_HDR_TSL: TSL mode
>>    */
>>   enum i3c_hdr_mode {
>> +    I3C_SDR,
>>       I3C_HDR_DDR,
>>       I3C_HDR_TSP,
>>       I3C_HDR_TSL,
>> @@ -53,6 +55,7 @@ enum i3c_hdr_mode {
>>   /**
>>    * struct i3c_priv_xfer - I3C SDR private transfer
>>    * @rnw: encodes the transfer direction. true for a read, false for a write
>> + * @cmd: Read/Write command in HDR mode, read: 0x80 - 0xff, write: 0x00 - 0x7f
>>    * @len: transfer length in bytes of the transfer
>>    * @actual_len: actual length in bytes are transferred by the controller
>>    * @data: input/output buffer
>> @@ -61,7 +64,10 @@ enum i3c_hdr_mode {
>>    * @err: I3C error code
>>    */
>>   struct i3c_priv_xfer {
>> -    u8 rnw;
>> +    union {
>> +        u8 rnw;
>> +        u8 cmd;
>> +    };
>>       u16 len;
>>       u16 actual_len;
>>       union {
>> @@ -301,6 +307,10 @@ int i3c_device_do_priv_xfers(struct i3c_device *dev,
>>                    struct i3c_priv_xfer *xfers,
>>                    int nxfers);
>>   +int i3c_device_do_priv_xfers_mode(struct i3c_device *dev,
>> +                  struct i3c_priv_xfer *xfers,
>> +                  int nxfers, enum i3c_hdr_mode mode);
>> +
>>   int i3c_device_do_setdasa(struct i3c_device *dev);
>>     void i3c_device_get_info(const struct i3c_device *dev, struct i3c_device_info *info);
>> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
>> index 12d532b012c5a..352bd41139569 100644
>> --- a/include/linux/i3c/master.h
>> +++ b/include/linux/i3c/master.h
>> @@ -472,6 +472,9 @@ struct i3c_master_controller_ops {
>>       int (*priv_xfers)(struct i3c_dev_desc *dev,
>>                 struct i3c_priv_xfer *xfers,
>>                 int nxfers);
>> +    int (*priv_xfers_mode)(struct i3c_dev_desc *dev,
>> +                   struct i3c_priv_xfer *xfers,
>> +                   int nxfers, enum i3c_hdr_mode mode);
>>       int (*attach_i2c_dev)(struct i2c_dev_desc *dev);
>>       void (*detach_i2c_dev)(struct i2c_dev_desc *dev);
>>       int (*i2c_xfers)(struct i2c_dev_desc *dev,
>>
> 
>